One type of illuminated sign which is in use at the present time has a housing provided with an open front or an open front and an open rear and containing within the housing a florescent light fitting. The open front of the housing is provided with a cover in the form of a frame, which is pivotally connected along the top of the frame to the top of the housing, and a screen of rigid sheet material covering an opening defined by the frame, the periphery of the sheet material being secured to the frame. The frame is made of extruded metal sections which are connected together, at the corners of the frame, by L-shaped connectors engaging in the extruded metal sections. The rigid sheet material of the screen is light-transmitting and has either opaque insignia thereon or an opaque zone surrounding light-transmitting insignia. In the case of the housing having open rear, a similiar frame and screen are provided at the rear of the housing. Such screens are normally made of glass.
An illuminated sign of this type is disclosed in my co-pending U.S. patent application Ser. No. 050,362 filed June 20, 1979, the disclosure of which is incorporated herein by reference.
The use of glass for the screens of such signs is expensive and, moreover, glass sign screens are fragile and can easily be broken by accident or by vandals.